UNIT 8: GENETICS AND INHERITANCE
Mendel and the Gene Idea (Ch. 11)
The difference between alleles and genes
● Alleles are different types of genes
● Ex: homologous chromosomes have the same gene(flower color) but different alleles
(types of flower color ⇒ purple vs white)
Vocabulary such as homozygous, heterozygous, phenotype, and genotype
● Homozygous: two dominant alleles, two recessive alleles
● Heterozygous: two different alleles
● Phenotype: physical trait based off of the genes
● Genotype: genetic structure based off of genes
How to use Punnett squares for monohybrid crosses
Examples and distinctions between incomplete and codominance
● Incomplete: two traits mix together
→ red colored flower + white colored flower = pink flower
● Codominance: traits coexist on the same organism
→ red colored flower + white colored flower = red flower with white spots or white
flower with red spots
Law of Segregation
● During the formation of a gamete, each gene separates from each so that each gamete
carries only one allele for each gene
How to analyze and create pedigrees
● Circle: female
● Square: male
● Shaded: exhibits the trait
Mendel’s experiment involving the P, F1, and F2
generations
● Mendel’s experiment: experimented with one
characteristic of a pea plant at a time
● Grandparent plants: P
● Offspring of P gen are (Parent plant): F1
● Offspring of F1 (grandparent): F2
● All of F1 had purple flowers ⇒ mendel
allowed f2 to self pollinate ⇒ some of the
f2 generation had white flowers (every 3
purple flowered plants there was an average
of 1 white flowered plant)
● Law of Segregation: same experiment for all
7 pea plant characteristics, in each case, 1
value of the characteristic disappeared in
the F1 plant and showed up again in the F2 plants. In each case, 75% of F2 plants
had one value of the characteristic and 25% had the other value
● Law states that there are 2 factors controlling a given characteristic, one of which
dominates the other, and these factors separate and go to different gametes when a
parent reproduces.
● Video notes:
○ Mendel combined purebred yellow-seeded plant w/ purebred green-seeded plant
and got only yellow seeds ⇒ yellow trait was dominant
○ Yellow seeded hybrid plant self pollinated and got 1 green out of 3 yellow ⇒
green trait was hidden by the dominant yello2 ⇒ recessive
Mendel and the Gene Idea (Ch. 11)
The difference between alleles and genes
● Alleles are different types of genes
● Ex: homologous chromosomes have the same gene(flower color) but different alleles
(types of flower color ⇒ purple vs white)
Vocabulary such as homozygous, heterozygous, phenotype, and genotype
● Homozygous: two dominant alleles, two recessive alleles
● Heterozygous: two different alleles
● Phenotype: physical trait based off of the genes
● Genotype: genetic structure based off of genes
How to use Punnett squares for monohybrid crosses
Examples and distinctions between incomplete and codominance
● Incomplete: two traits mix together
→ red colored flower + white colored flower = pink flower
● Codominance: traits coexist on the same organism
→ red colored flower + white colored flower = red flower with white spots or white
flower with red spots
Law of Segregation
● During the formation of a gamete, each gene separates from each so that each gamete
carries only one allele for each gene
How to analyze and create pedigrees
● Circle: female
● Square: male
● Shaded: exhibits the trait
Mendel’s experiment involving the P, F1, and F2
generations
● Mendel’s experiment: experimented with one
characteristic of a pea plant at a time
● Grandparent plants: P
● Offspring of P gen are (Parent plant): F1
● Offspring of F1 (grandparent): F2
● All of F1 had purple flowers ⇒ mendel
allowed f2 to self pollinate ⇒ some of the
f2 generation had white flowers (every 3
purple flowered plants there was an average
of 1 white flowered plant)
● Law of Segregation: same experiment for all
7 pea plant characteristics, in each case, 1
value of the characteristic disappeared in
the F1 plant and showed up again in the F2 plants. In each case, 75% of F2 plants
had one value of the characteristic and 25% had the other value
● Law states that there are 2 factors controlling a given characteristic, one of which
dominates the other, and these factors separate and go to different gametes when a
parent reproduces.
● Video notes:
○ Mendel combined purebred yellow-seeded plant w/ purebred green-seeded plant
and got only yellow seeds ⇒ yellow trait was dominant
○ Yellow seeded hybrid plant self pollinated and got 1 green out of 3 yellow ⇒
green trait was hidden by the dominant yello2 ⇒ recessive
